Liquid crystal panels are used in display devices in televisions, mobile phones such as smartphones, mobile computing devices, and the like. To display images, liquid crystal panels need to use external light. Therefore, as described in Patent Document 1, display devices of this type include a liquid crystal panel as well as an illumination device (a so-called backlight device) for supplying light to the liquid crystal panel. This illumination device is arranged on the rear surface side of the liquid crystal panel and is configured to emit light that is spread out in a planar manner towards the rear surface of the liquid crystal panel.
As described in Patent Document 1, one well-known example of such an illumination device is the so-called edge-lit (or side-lit) type, which includes a light guide plate constituted by a transparent rectangular plate-shaped member and a light source unit arranged facing an end face of the light guide plate. The end face of the light guide plate functions as a light-receiving portion into which light emitted from the light source unit enters, and the front surface of the light guide plate functions as a light-exiting portion which allows the light that entered via the light-receiving portion to exit.
In recent years, configurations (hereinafter, “LED units”) in which a plurality of light-emitting diodes (LEDs) are mounted on an elongated LED substrate have been widely used as light source units in this type of illumination device.
Moreover, due to design diversification and the like, in recent years there has been demand for display devices having display surfaces of various shapes other than just rectangular shapes. Therefore, there has also been demand for illumination devices of various shapes as well.